Semiconductor device manufacturing apparatus employing vacuum system

ABSTRACT

An apparatus for manufacturing a semiconductor device employs a vacuum system, in which a heating source is installed in a predetermined portion of a venting-gas inlet. A venting-speed controlling valve is installed in a predetermined portion of an exhaust pipe, for controlling the speed of gas flowing from a load lock chamber to a pump by controlling the opening and closing thereof. An exhaust pipe may have a main pipe with different diameters in different portions to reduce the venting speed. Accordingly, condensation-induced particle formation can be reduced by thus preventing adiabatic expansion of the gas in a load lock chamber.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of Ser. No.08/752,954, which was filed on Nov. 20, 1996, and which issued as U.S.Pat. No. 5,833,425, on Nov. 10, 1998.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for manufacturing asemiconductor device. More particularly, it relates to an apparatus formanufacturing a semiconductor device, wherein the apparatus employs avacuum system.

In the fabrication of a semiconductor device using an apparatusemploying a vacuum system, particles are formed during thepressure-reduction (pump down) of a process chamber and the particlesformed thus settle on wafers being processed therein. Such particulatecontamination of a semiconductor wafer significantly lowers the productyield and the reliability of a semiconductor device. This problembecomes more severe with increasing wafer diameters and with higherintegration levels.

Particle formation during pressure-reduction or venting is attributed toa condensation mechanism caused by an adiabatic expansion of gas (see"Condensation-Induced Particle Formation During Vacuum Pump Down" by YanYe et al., Journal of the Electrochemical Society, Vol. 140, No. 5, pp.1463-1468, May 1993). According to the suggested mechanism, a rapid dropin the pressure of a process chamber causes gas in the chamber toundergo adiabatic expansion and causes its temperature to fall rapidly.The gas is simultaneously condensed into water droplets. During dropletformation, such gases in the air as SO₂, O₃, H₂ O and other gaseousimpurities tend to diffuse into the droplets and thus become absorbed.

Due to the thermal capacity of the chamber walls being greater than thatof the droplets, which are formed as described above, the inner surfacetemperature of the chamber decreases more slowly than does thetemperature of the droplets. This resulting temperature differencecauses heat to be transferred from the chamber to the droplets. Suchheat transfer leads to a cycle of heating, evaporation and condensationof the droplets and causes an increase in the concentration ofimpurities in the liquid droplets. During the concentrated liquid phase,when the concentration of H₂ O₂ in the liquid is high enough, theformation of sulfuric acid droplets occurs. Namely, H₂ O₂ of the liquidquickly reacts with SO₂ from the liquid or air to form sulfuric acidand, as the droplets continue their evaporation/condensation cycle,residue particles which are spherical in shape and contain mainlysulfuric acid are formed.

The main elemental components of the residue particles, which are formedby the evaporation/condensation cycles are carbon, sulfur and oxygen.The residue particles are quite stable thermodynamically and do notcompletely evaporate even upon heating to temperatures as high as 180°C.

As the size of the process chamber is decreased the relative humidity ofthe gas increases and depressurizing speed or venting speed alsoincreases. This leads to an increase in the number ofcondensation-induced particles that are formed.

FIG. 1 is a schematic view of an ion-implanting apparatus, in aconventional apparatus for manufacturing semiconductor devices, whichemploys a vacuum system. In FIG. 1, a reference numeral 10 denotes aprocess chamber for ion-implanting a semiconductor wafer therein;reference numeral 20 denotes two load lock chambers communicating withpredetermined portions of the process chamber 10, for loading wafers tobe transferred to the process chamber therein; reference numeral 30denotes an isolation valve installed between the process chamber 10 andeach of the load lock chambers 20, for providing isolation of theprocess chamber 10 from the load lock chambers 20; reference numeral 40denotes a pump for reducing the pressure of the load lock chambers 20 totransfer the wafers to the process chamber 10 in a state of vacuum;reference numeral 50 denotes an exhaust pipe having two sub-pipes Aconnected to the respective load lock chambers 20 and a main pipe B ofwhich one end is connected to the sub-pipes A and the other end isconnected to the pump 40; and reference numeral 60 denotes two shut-offvalves, one of which is installed in a predetermined portion in each ofthe sub-pipes A, for providing a shut-off of the flow of gas from theload lock chambers 20 to pump 40.

In the device of FIG. 1, an air valve, which is opened and closeddepending on gas pressure, is usually used as the shut-off valve 60. Thediameter of the main pipe B is larger than that of the sub-pipes A,since gas flowing from the load lock chambers 20 is collected in andpassed through the main pipe B. Also, reference numeral 70 denotes aninlet for injecting venting-gas into the load lock chambers 20. Theoperation of a conventional apparatus for manufacturing a semiconductordevice by employing a vacuum system will now be described in furtherdetail while referring to FIG. 1.

The exhaust pipe 50 installed between the shut-off valves 60 and pump 40is maintained in a low vacuum of about 10⁻³ Torr. Wafers are then loadedin the load lock chambers 20, and the shut-off valves 60 are opened todrop the pressure of the load lock chambers 20 to about 10⁻³ Torr.Thereafter, the wafers are transferred to the process chamber 10 byopening the isolation valves 30. Such process chamber 10 is maintainedat a high vacuum of about 10⁻⁶ Torr during the processing of wafers.

The load lock chambers 20 are set to the lower vacuum to avoid a suddenturbulence of gas and to reduce the preliminary formation of particlesbefore the wafers are transferred to the process chamber 10. Suchformation of particles is minimized by reducing the difference betweenthe high vacuum of the process chamber 10 and atmospheric pressure ofthe load lock chambers 20.

FIG. 2 is a sectional magnified view of the air valve which is used as ashut-off valve 60. In FIG. 2, a reference numeral 100 denotes acylindrical case having a first orifice on its side and a second orificeon its base; reference numeral 200 denotes a board installed in apredetermined location inside of the case 100 to divide it into an upperportion and a lower portion and having a hole in the center thereof forcommunicating the lower portion of the case 100 with the upper portionof the case 100; reference numeral 300 denotes a bellows fixed to theboard 200 and surrounding the center hole thereof which is sealed bybeing attachably fixed to the lower surface of the board and having anO-ring on the lower end portion thereof, to provide a means for openingand closing the second orifice at the base of the case 100; referencenumeral 500 denotes an elastic rubber boot installed on the internalupper surface of the case 100 and extending in a convex manner in thedirection of the lower portion of the case 100; reference numeral 600denotes a spring support fixed to the convex surface of the rubber boot500, one portion thereof being inserted into the hole of the board 200;reference numeral 700 denotes a spring, one end of which is fixed to abase 400 of the bellows 300 and the other end of which is fixed to thespring support 600; reference numeral 800 denotes an air inletcommunicating with a side portion of the upper portion of the case 100;and reference numeral 900 denotes the flow of gas from the load lockchambers 20 via the first orifice located on the side of the case 100 tothe pump 40 (FIG. 1) via the second orifice located in the base of thecase 100.

If the pressure of air injected through the air inlet 800 is below apredetermined value, the second orifice located at the base of the case100 is opened by the base 400 of the bellows 300. If the air pressure isgreater than or equal to the predetermined pressure, the convex endportion of the rubber boot 500 is pushed upward, vertically contractingthe bellows 300 and thus closing the second orifice at the base of thecase 100. Since the second orifice is quickly opened, the pressure ofthe load lock chambers 20 also rapidly drops.

FIGS. 3A and 3B show scanning electron microspectroscopy (SEM)photographs of particles formed in the load lock chambers 20. Theparticles are about 0.3 μm to 3.7 μm in diameter and generally sphericalin shape.

FIG. 4 illustrates the result obtained by analyzing the components ofthe particles of FIGS. 3A and 3B by Auger electron spectroscopy (AES).The main components, as shown by the elemental analysis graph of FIG. 4,are sulfur, oxygen and carbon.

As described above, in the conventional apparatus for manufacturing asemiconductor device by employing a vacuum system, gas condensation isfound to be the cause of particle formation. This conclusion issupported by an analysis of the shape and components of particlesgenerated in the load lock chambers, as suggested by Yan Ye et al. Inother words, as the shut-off valves installed on the exhaust pipe forexhausting the load lock chambers of gas are rapidly opened, thepressure of the load lock chambers drops quickly. Therefore, particleformation is attributed to adiabatic expansion of the gas in the loadlock chambers.

By the same mechanism as described above, the adiabatic expansion ofventing-gas also produces particles during the venting of the load lockchambers.

SUMMARY OF THE INVENTION

One object of the present invention is to provide an apparatus formanufacturing a semiconductor device, wherein the apparatus can reducecondensation-induced particle formation by preventing adiabaticexpansion of the gas in a load lock chamber of the apparatus.

To achieve one aspect of the above object, there is provided anapparatus according to a first embodiment of the present invention formanufacturing a semiconductor device, said apparatus comprising: aprocess chamber for fabricating a semiconductor device therein; a loadlock chamber communicating with a predetermined portion of the processchamber, for loading a semiconductor wafer to be transferred to theprocess chamber therein; a pump for reducing the pressure of the loadlock chamber; an exhaust pipe connecting the load lock chamber with thepump, for exhausting gas of the load lock chamber; and a valve installedin a predetermined portion of the exhaust pipe, wherein the valve is aventing speed controlling valve for controlling the speed of gas flowingfrom the load lock chamber to the pump.

To achieve another aspect of the above object, there is provided anapparatus according to a second embodiment of the present invention formanufacturing a semiconductor device, said apparatus comprising: aprocess chamber for fabricating a semiconductor device therein; a loadlock chamber communicating with the process chamber, for loading asemiconductor wafer to be transferred to the process chamber therein;and a venting-gas inlet for injecting venting gas into the load lockchamber, wherein the venting-gas inlet is provided with a heating sourceinstalled in a predetermined portion thereof, for heating venting gasinjected into the load lock chamber.

To achieve yet another aspect of the above object, there is provided anapparatus according to a third embodiment of the present invention formanufacturing a semiconductor device, said apparatus comprising: aprocess chamber for fabricating a semiconductor device therein; aplurality of load lock chambers communicating with predeterminedportions of the process chamber, for loading semiconductor wafers to betransferred to the process chamber therein; a pump for reducing thepressure of the plurality of load lock chambers; an exhaust pipeconnecting the load lock chambers with the pump, for exhausting gas ofthe load lock chambers, the exhaust pipe comprising a plurality ofsub-pipes, each sub-pipe being connected to each load lock chamber, anda main pipe having a first predetermined portion different from a secondportion in diameter, one end thereof being connected to the plurality ofsub-pipes and the other end being connected to the pump; and a valveinstalled in a predetermined portion of the exhaust pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

The above object and advantages of the present invention will becomemore apparent by describing in detail preferred embodiments thereof withreference to the attached drawings in which:

FIG. 1 is a schematic view of a conventional apparatus for manufacturinga semiconductor device, wherein the apparatus employs a vacuum system;

FIG. 2 is a sectional view of an air valve, which is used as a shut-offvalve as depicted in FIG. 1;

FIGS. 3A and 3B show SEM photographs of particles generated in the loadlock chambers of FIG. 1;

FIG. 4 shows the result from an AES analysis of the components of theparticles of FIGS. 3A and 3B;

FIG. 5 is a schematic view of an apparatus according to an embodiment ofthe present invention for manufacturing a semiconductor device;

FIG. 6 is a schematic view of a throttle valve used as a venting speedcontrolling valve as shown in FIG. 5;

FIG. 7 is a schematic view of an apparatus according to a secondembodiment of the present invention for manufacturing a semiconductordevice; and

FIG. 8 is a schematic view of an apparatus according to a thirdembodiment of the present invention for manufacturing a semiconductordevice.

DETAILED DESCRIPTION OF THE INVENTION Embodiment 1

FIG. 5 is a schematic view of a semiconductor device manufacturingapparatus, especially, an ion-implanting device, according to a firstembodiment of the present invention. Here, a reference numeral 11denotes a process chamber for ion-implanting a semiconductor wafertherein; reference numeral 21 denotes a plurality of, for example, twoload lock chambers communicating with predetermined portions of theprocess chamber 11, for loading semiconductor wafers to be transferredto the process chamber therein; reference numeral 31 denotes anisolation valve disposed between the process chamber 11 and each loadlock chamber 21, for isolating of the process chamber 11 from the loadlock chambers 21; reference numeral 41 denotes a pump for reducing thepressure of the load lock chambers 21 to transfer the wafers from theload lock chambers 21 to the process chamber 11 in vacuum; referencenumeral 51 denotes an exhaust pipe having a plurality (e.g., two) ofsub-pipes C, each sub-pipe being connected to each load lock chamber 21,and a main pipe D with a first end which is connected to the sub-pipes Cand having a second end which is connected to pump 41; reference numeral61 denotes a venting speed controlling valve installed to the exhaustpipe 51, for controlling the speed of the flow of gas from the load lockchambers 21 to the pump 41 by controlling the opening thereof; andreference numeral 71 denotes a venting-gas inlet for injectingventing-gas into each load lock chamber 21.

Preferably, the diameter of main pipe D is larger than that of thesub-pipes C, since gas flowing from the load lock chambers 21 arecollected in and pass through the main pipe D. Further, a throttle valvemay be used as the venting speed controlling valve 61.

According to this embodiment, condensation-induced particle formationcan be reduced by steadily increasing a venting speed with the ventingspeed controlling valve 61. In such a manner adiabatic expansion of gasis prevented by avoiding a rapid drop of pressure in the load lockchambers 21. In addition, condensation-induced particle formation canalso be reduced by providing a heating source, for example, heater line81 installed in a predetermined portion of the venting gas inlet to heatup gas injected during a venting process. Such a heating procedure isadapted to reduce the relative humidity of the venting gas and toconsequently reduce liquid produced by condensation of water vapor inthe gas.

FIG. 6 is a schematic view of a throttle valve used as the venting-speedcontrolling valve 61. In FIG. 6, a reference numeral 101 denotes acylindrical case having orifices in the sides thereof, through which thecylindrical case 101 is connected to the exhaust pipe 51 of FIG. 5;reference numeral 201 denotes a disk-shaped rotational plate fordividing case 101 into left and right portions; and reference numeral301 denotes a rotational shaft being rotated by a motor (not shown)which is connected with the rotational plate 201 and adapted tovertically penetrate through the case 101 and pass through the center ofthe rotational plate 201. Thus, the rotational plate 201 is rotated bythe rotation of the rotational shaft 301 with the rotational shaftserving as the axis. The speed of gas flowing from the load lockchambers 21 to pump 41 (FIG. 5) can be controlled by varying therotational speed of the rotational shaft 301.

Embodiment 2

FIG. 7 is a schematic view of an apparatus according to a secondembodiment of the present invention for manufacturing a semiconductordevice, especially a device produced by using an ion-implanting processstep. Like reference numerals of FIG. 5 denote the same elements in FIG.7. Reference numeral 61A denotes a shut-off valve installed in apredetermined portion of the sub-pipe C, to provide a means to shut-offthe flow of gas from the load lock chambers 21 to the pump 41. An airvalve, for example, can be used as a shut-off valve. A reference numeral81 denotes a heating source installed in a predetermined portion of theventing-gas inlet 71. A heating line, for example, can be used as theheating source. The heating source 81 heats up venting gas beinginjected into the load lock chambers 21 to decrease the relativehumidity of the venting gas. Hence, this heating procedure reduces theformation of condensation-induced particles in the load lock chambers21.

Embodiment 3

FIG. 8 is a schematic view of an apparatus according to a thirdembodiment of the present invention for manufacturing a semiconductordevice, especially a device produced by using an ion-implanting processstep. Like reference numerals of FIG. 5 denote the same elements in FIG.8. A reference numeral 51A denotes an exhaust pipe having a plurality ofpipes, for example, two sub-pipes E, and a main pipe F. In FIG. 8, eachsub-pipe is connected to each load lock chamber 21. The main pipe F hasa first end connected to the sub-pipes E and a second end connected tothe pump 41. Main pipe F has a first diameter for a predetermined lengthfrom the first portion where the plurality of sub-pipes meet and has asecond diameter in the second portion connected to the pump 41.

Preferably, the main pipe F has a first diameter for a predeterminedlength from where the sub-pipes E meet, while it has a second diameterlarger than the first diameter in the second portion thereof. Theportion of main pipe F having the first diameter is just an example ofapplying such a concept. Thus, the position of the first diameterportion can be modified, if necessary, to achieve optimum results.Further, the first diameter is preferably larger than that of thesub-pipes E.

A reference numeral 61A denotes a shut-off valve installed in apredetermined portion of the sub-pipes E to provide a means to shut-offthe flow of gas from the load lock chambers 21 to the pump 41. An airvalve can be used as the shut-off valve. The shut-off valve 61A ispreferably installed in a predetermined portion of the sub-pipes E.Therefore, even though the shut-off valves 61A can be opened suddenly,the speed of exhausted gas can be reduced due to the portion of thefirst diameter in the main pipe F. As a result, condensation-inducedparticle formation can be reduced by preventing an adiabatic expansionof gas caused by a rapid drop in the pressure of the load lock chambers21.

In addition, condensation-induced particle formation can also be reducedby providing a heating source (similar to that shown in FIG. 7), forexample, a heating line 81, in a predetermined portion of theventing-gas inlet. This further minimizes the formation of undesiredparticles by reducing the relative humidity of the venting gas andconsequently reducing the amount of water vapor available to condenseinto droplets.

As described above, according to the preferred embodiments of thepresent invention, condensation-induced particle formation can bereduced by preventing adiabatic expansion of gas.

While this invention has been described with respect to that which ispresently considered to be the most practical and preferred embodiments,the invention is not limited to such disclosed embodiments. It isclearly understood that many variations can be possible within the scopeand spirit of the present invention by any one skilled in the art. Infact, it is intended that the present invention cover variousmodifications and equivalent arrangements within the spirit and scope ofthe appended claims.

What is claimed is:
 1. An apparatus for manufacturing a semiconductor,said apparatus comprising:a process chamber for fabricating asemiconductor device therein; a plurality of load lock chambers adaptedfor communicating with predetermined portions of said process chamber,and adapted for loading semiconductor wafers to be transferred to withinsaid process chamber; a pump adapted for reducing the pressure of saidplurality of load lock chambers; an exhaust pipe connecting said loadlock chambers with said pump, and adapted for exhausting gas of saidload lock chambers, said exhaust pipe comprising a main pipe and aplurality of sub-pipes, wherein each sub-pipe has a first end connectedto one of said plurality of load lock chambers, and a second endconnected to said main pipe, and said main pipe has a first portionhaving a first diameter and a second portion having a second diameterlarger than said first diameter, said first portion comprising anunbranched section of the main pipe extending from a point where themain pipe branches to connect to said plurality of sub-pipes, and thesecond portion comprising an unbranched section of the main pipeextending from the first section to a point where the main pipe connectsto said pump; and a valve installed in a predetermined portion of saidexhaust pipe.
 2. An apparatus as claimed in claim 1, for manufacturing asemiconductor device, wherein said first portion of the main pipe has apredetermined length.
 3. An apparatus as claimed in claim 1, formanufacturing a semiconductor device, wherein said valve is installed ina predetermined portion of a sub-pipe.
 4. An apparatus as claimed inclaim 1, for manufacturing a semiconductor device, wherein each of saidload lock chambers comprises:a venting-gas inlet adapted for injectingventing gas into said load lock; and a heating source installed in apredetermined portion of said venting-gas inlet.
 5. An apparatus asclaimed in claim 1, for manufacturing a semiconductor device, whereinsaid valve is a shut-off valve.
 6. An apparatus as claimed in claim 5,for manufacturing a semiconductor device, wherein said shut-off valve isan air valve.